var page = require('webpage').create();
console.log('The default user agent is ' + page.settings.userAgent);
page.settings.userAgent = 'SpecialAgent';
page.open('http://www.httpuseragent.org', function (status){
  if(status !== 'success'){
    console.log('Unable to access network');
  } else {
    var ua = page.evaluate(function(){
      return document.getElementById('myagent').textContent;
    });
    console.log(ua);
  }
  phantom.exit();
});
